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Studies on Host Preference of Trichogramma Zahiri

Md. Nazmul Bari
Senior Scientific Officer
Entomology Division, BRRI, Gazipur-1701

Dr. Mahbuba Jahan
Professor
Department of Entomology, BAU, Mymensingh-2202

Abstract/ Executive Summary:

Host preference studies of T. zahiri on rice hispa eggs clearly indicated that it was a parasitoid of fresh eggs of the pest. In a choice test, T. zahiri showed a clear preference for 6 to 24h old eggs than 48 and 72 hours old eggs.

Keywords: Trichogramma zahiri, Parasitoid, Host preference and Rice hispa

Location: BRRI, Gazipur

Start Date: 01-07-2010

End Date: 30-06-.2011

Program Area: Pest Management

Commodity: Rice

Objectives:

To evaluate possible preference of the parasitoids for a specific host stage

Methodology:

The choice test of the parasitoid the experiment was conducted by placing rice hispa egg of four age group (age class- 6hr, 24hr, 48hr and 72hr) in a test tube (23X8cm²). Four rice leaf pieces having 10 hispa eggs of four age groups were placed in each test tube with a water soaked cotton wool for maintaining leaf turgidity. The leaf pieces with different ages of rice hispa eggs marked separately with permanent CD marker. A single female parasitoid, T. zahiri was released in the test tube to parasitize the hispa egg according it´s choice. The parasitoids were allowed to parasitize them for 24 hours at about 25⁰C temperature in the laboratory. Both the ends of the test tube were covered by the black cloth except the area where the eggs were present. Dark shedding forced the parasitoid to remain active around lightened area where host eggs were available. The rice leaf with parasitized hispa eggs were kept in the test tubes for about 5 days. Then the eggs were examined under a microscope to determine the parasitism rate of different ages of the host eggs. The parasitized eggs were kept individually in a 5 ml glass vial and checked daily for adult emergence. The sex ratios of the emerged adults were determined. The experiment was replicated 10 times and 10 parasitoids were used in each time. Thus 100 parasitoids were used in this study which gave 100 replications.

Source of Information: Internal Review Workshop, 2010-11

Article Link (Online Journal):

Funding Source:

1.	Budget:
2. Bangladesh Agricultural Research Council	Budget:

Total Budget (Tk.) :

Achievement/Findings:

Parasitism by T. zahiri differed significantly among the age of different rice hispa (RH) egg showing a range of 2.2 to 55.1%. The highest percentage of egg parasitism was observed in 6 hours old host egg 55.1% which followed 51.8% in 24 hours old host. Parasitism was very low in fairly old host. On an average 9.9 and 2.2% parasitism occurred in 48 and 72 hours old eggs respectively. The study clearly indicated that the parasitoid, T. zahiri preferred younger eggs rather than the older ones. It was noted that there was no significant difference in the performance of the parasitoid when the eggs were 6 and 24 hours old. On the other hand significantly lower rate of parasitism 9.9 and 2.2% found in 48 and 72 hours old host eggs respectively. The sex ratio was female biased (71.79–76.25%) irrespective of different ages of host but there was no significance difference.

Knowledge Management: Report/Proceedings